No Smoking Gun Tying Russia to Spear-Phishing Attack, Microsoft Says

There is not enough evidence to attribute a recent wave of spear-phishing emails impersonating personnel at the United States Department of State to Russian hackers, Microsoft says.

The attack, which started on November 14, was previously said to have been the work of Cozy Bear, a Russian threat actor involved in hacking incidents during the 2016 U.S. presidential election. Microsoft, which tracks the adversary as YTTRIUM, begs to differ.

“Microsoft does not yet believe that enough evidence exists to attribute this campaign to YTTRIUM,” the software giant says.

The recently observed spear-phishing emails targeted public sector institutions and non-governmental organizations like think tanks and research centers, but also hit educational institutions and private-sector corporations in the oil and gas, chemical, and hospitality industries.

The campaign, which closely resembled attacks attributed to nation-states, targeted thousands of individual recipients in hundreds of organizations. Although distributed around the world, most of the targets are located in the United States, while others are in Europe, Hong Kong, India, and Canada.

Impersonating the identity of individuals working at the United States Department of State, the spear-phishing emails mimicked sharing notifications from OneDrive. Once the recipient clicked a link in the emails, however, an exploitation chain leading to the installation of a DLL backdoor would start.

The emails contained a link leading to a legitimate but compromised website, and also containing random strings which Microsoft believes were likely used to identify distinct targeted individuals who clicked on the link.

As soon as the user clicked on the link, a ZIP archive containing a malicious Windows shortcut (.LNK) file was delivered. The LNK file executed an obfuscated PowerShell command to extract a base64-encoded payload from within the LNK itself.

This encoded payload, another heavily obfuscated PowerShell script, would fetch two additional resources from within the .LNK file. The second stage in this attack was an instance of Cobalt Strike, a commercially available penetration testing tool.

A third-stage was also used, in the form of a PE file with a Meterpreter header, which gets loaded and connects to a command-and-control (C&C) server address found inside configuration info in the PE file.

A feature-rich penetration testing tool, Cobalt Strike provides attackers with remote access to the infected computer. Some of the capabilities available to attackers include reconnaissance, privilege escalation, keylogging, execution of arbitrary commands through PowerShell or WMI, and the downloading and installation of additional malware.